1. Field of the Invention
The present general inventive concept relates to a mounting structure for an integrated circuit in which an element which is sensitive to an ambient temperature and a temperature in operation (hereinbelow, referred to as a ‘temperature-sensitive element’), and an element which generates heat during the operation (hereinbelow, referred to as ‘heating element’) mixedly exist.
2. Description of the Related Art
An integrated circuit is composed by mounting a plurality of elements selected for certain desired functions on a printed circuit board (PCB). A lifespan of a temperature-sensitive element such as an electrolytic capacitor is considerably influenced by an ambient temperature and a temperature in operation.
The electrolytic capacitor in the integrated circuit is generally used for smoothing electric power. The electrolytic capacitor uses a thin oxidation film for a dielectric thereof, and aluminum for an electrode thereof. Since the dielectric can be formed very thin, the capacitor can obtain a greater capacity compared to its volume.
A ceramic capacitor uses a material of a high inductivity, such as a titanium-barium as for a dielectric element between electrodes. Since inductance is low in the ceramic capacitor, the ceramic capacitor has a good high-frequency property, and therefore, it is often used in a bypass of a high frequency.
In a general integrated circuit, a plurality of capacitors are disposed in parallel at the nearest location from a power pin of respective elements in order to guarantee a normal operation of the elements. Also, the electrolytic capacitor is disposed near a power source to reduce ripples of a power part, thereby stably supplying the power.
FIG. 1 is a plan view illustrating a mounting structure of a general integrated circuit. On the PCB 10, a central processing unit (CPU) 20, a voltage regulator 30, a motor driver 40, an interface 50 and a memory 60 are properly disposed.
The CPU 20, the voltage regulator 30, the motor driver 40, the interface 50 and the memory 60 are respectively connected to one or more ceramic capacitors 21, 31, 41, 51, and 61 and electrolytic capacitors 32, 42, 52 and 62.
The electrolytic capacitor, for example, an electrolytic capacitor 32 connected to an output terminal of the voltage regulator 30 is dedicated to restrain fluctuation of an output voltage according to an immediate change of a load.
The electrolytic capacitor is used not only at a power terminal but also near an element which is far from a power source, for an optimal operation of the element. Especially, the electrolytic capacitor 42 is always used near a power pin of the motor driver 40 which consumes a lot of electric current at once when starting its driving.
For an optimal power-smoothing effect, the electrolytic capacitors 32 to 62 are disposed as near the power pin of the element as possible.
A lifespan of the electrolytic capacitors 32 to 62 largely depends on the ambient temperature and the temperature in operation. FIG. 2 is a graph illustrating the lifespan changing according to the temperature of the electrolytic capacitor 32 to 62. As shown in FIG. 2, the temperature of every electrolytic capacitor 32 to 62 remarkably decreases at a high temperature.
However, in general integrated circuits, especially in the mounting structure of the integrated circuit where a temperature-sensitive element and a heating element compatibly exist, the heating elements, such as the voltage regulator 30 and the motor driver 40, and the electrolytic capacitors 32 and 42 are disposed regardless of the sensitivity of the temperature-sensitive element, as shown in FIG. 1.
Therefore, as the heat generated from the heating elements 30 and 40 are transmitted to the electrolytic capacitors 32 and 42, that are the temperature-sensitive elements, the temperature in operations of the electrolytic capacitors 32 and 42 increase, thereby shortening the lifespan of the electrolytic capacitors 32 and 42. As a result, the lifespan of the whole device becomes short, and a solution for guaranteeing a long lifespan of the electrolytic capacitor 32 and 42 is required.